The invention pertains to a clamping jaw for a jaw chuck and, more particularly, a clamping jaw having a clamping surface comprising hard metal particles.
Jaw chucks for drills, lathes or milling machines are known. They contain clamping jaws that can be adjusted with respect to their distance from one another in order to clamp in position a usually cylindrical tool (tool shaft) or work piece. The clamping jaws of high-quality jaw chucks contain a base body of steel, the clamping surface of which is provided with a plate, strip or the like of hard metal in order to reduce the wear. This hard metal part is connected to the base body by means of hard soldering. The clamping surface of the clamping jaw represents the surface or edge which adjoins the tool or work piece when the tool or work piece is clamped in position. The hard metal part reduces the wear of the clamping jaw and increases the clamping accuracy coaxially to the jaw chuck over an extended period of time and a corresponding number of clamping and releasing processes.
However, the different thermal expansions of hard metal and steel cause the clamping jaws to distort when they are cooled after the hard soldering process, i.e., the base body is bent. This is the reason why the base body is ground after the hard soldering process in order to achieve a high clamping accuracy. The subsequent grinding process has the disadvantage of an additional expenditure of labor. In addition, grinding tracks remain on the clamping jaw due to the subsequent grinding process, with said grinding tracks making it possible to recognize that the clamping jaw was subjected to a subsequent grinding process. This is undesirable for aesthetic reasons. The front end faces of clamping jaws that were subjected to a subsequent grinding process also appear differently large. This may be recognizable when the jaw chuck is assembled and the clamping jaws are moved toward one another. Even if a clamping jaw that was subjected to a subsequent grinding process is technically flawless, it may give rise to the impression that the clamping jaw represents a reject that was subsequently processed in order to be used after all. Consequently, it might appear that the quality of a subsequently ground clamping jaw is inferior.
It is an object of the present invention to provide a clamping jaw with a clamping surface that is equipped with a hard metal in which a subsequent grinding of the base body is not required.
The foregoing object is achieved by way of the present invention wherein the clamping surface of the clamping jaw is provided with hard metal particles instead of a continuous hard metal part. The hard metal particles are connected to the base body of the clamping jaw by means of hard soldering. The hard metal particles may consist of grains or a granulate of hard metal. The hard metal particles do not exert tension or pressure upon the base body of the clamping jaw as a result of different thermal expansions when the clamping jaw is cooled after the hard soldering process, i.e., the base body is not deformed. The dimensional accuracy of the clamping jaw according to the invention consequently is increased such that a subsequent grinding of the base body for achieving a sufficient dimensional accuracy is longer required.
Instead of using a base body of steel, the base body of the clamping jaw according to the invention may consist of the different metal.
In order to achieve a stable fit of a tool or work piece to be clamped in position, the hard metal particles provided on the clamping surface of the clamping jaw according to the invention are angular in preferred embodiments of the invention. The angular particles press against the clamped tool or work piece with their edges and corners and consequently hold the tool or work piece in a stable fashion.
In order to achieve a sufficiently high clamping accuracy, it may be required in embodiments of the invention to shape, in particular, grind, the particles that form the clamping surface after the hard soldering process. Under certain circumstances, a shaping of the clamping surface is not necessary if the hard metal particles were applied onto the clamping surface of the base body with a sufficient accuracy before the hard soldering process and did not change their position during the hard soldering process.